The present embodiments relate to volume rendering in medical imaging. For volume rendering, the transfer function specifies a mapping between the volumetric scalar data and the optical properties of the rendered image, such as color and opacity. In medical applications, task dependent transfer functions, also known as presets, are used to optimize the display of specific anatomical regions or to emphasize specific tissue types. Most volume rendering systems offer the functionality to manually adjust the parameters of the transfer function. The window width may specify the range of scalar values mapped and determines the contrast of the rendered image, and the window level centers the transfer function around a particular value of interest. Different combinations of the window width and level parameters lead to different findings and have to be adjusted repeatedly to improve the diagnostic information present in the image. Due to the complex and often unpredictable relationship between a transfer function and the resulting image, this manual adjustment is difficult and time consuming.
Automated techniques may simplify adjustment or setting of the transfer function. Image-driven approaches analyze the images generated with different parameters to select the optimal settings. For example, the user selects the best set of images, and a stochastic search is invoked to generate a new set of transfer functions based on the selection. Data-driven approaches analyze the volumetric data instead of the generated images. Although these approaches are widely used at research facilities, they are not commonly accepted in clinical practice as they are not intuitive or easy to use.